Cardiac rhythm or function management devices include implantable devices to help maintain heart rhythm or function. Such devices can include pacers, defibrillators, cardioverters, cardiac resynchronization therapy (CRT), or various combinations of such devices. Such devices can typically sense intrinsic heart contractions, deliver pacing pulses to evoke responsive heart contractions, or deliver a shock to interrupt certain arrhythmias. This can help improve the patient's heart rhythm or can help coordinate a spatial nature of the heart contraction, either of which may improve cardiac output of blood to help meet the patient's metabolic need for such cardiac output.
For example, detecting a ventricular tachyarrhythmia (e.g., a too-fast ventricular heart rhythm) often involves detecting a rate of ventricular heart contractions that exceeds a tachyarrhythmia rate threshold. By using multiple tachyarrhythmia rate thresholds, multiple tachyarrhythmia rate zones can be established, which can further classify different tachyarrhythmias based on which zone the heart rate falls within.
The present inventors have recognized that one problem with ventricular tachyarrhythmia detection is when an atrial pace is delivered at a heart rate that falls within one or more of the tachyarrhythmia rate zones. Such a “fast” atrial pace can inhibit detection of a tachyarrhythmic intrinsic ventricular contraction that occurs close in time to the fast atrial pace. This, in turn, can prevent proper diagnosis or treatment of a ventricular tachyarrhythmia. The present inventors have recognized an unmet need for improved apparatuses or methods for avoiding such problems.